[CRIU] --ext-mount-map auto likes MS_BIND too much

[Oleg Nesterov]

Hi Tycho,

Before anything else, let me remind that I do not really understand
this code.

Not only I am very new to criu, I know almost nothing about this
mount black magic. I still have no idea what this slave/shared/etc
actually means, and I am thinking in horror that sooner or later
I will need to read the docs ;)

That said.

On 04/14, Tycho Andersen wrote:
>
> > Perhaps resolve_external_mounts() should skip the fsroot_mounted() mount
> > points at least? Although afaics this is not enough too.
>
> I think we can't do an fsroot_mounted() check as we discussed here:
>
> http://lists.openvz.org/pipermail/criu/2015-April/019744.html

Thanks, will read tomorrow. But yes, yes, I understand that
fsroot_mounted() is not an option.

> but yes, something does look wrong :). In this case, the mounts are
> actually the same mounts, just in different namespaces. Perhaps
> mounts_equal()

As you already pointed out, this can't work. But let's ignore this.

Afaics, we obviously need the

	bool come_on_this_mount_doesn_t_need_external()

helper called by resolve_external_mounts(). But this is not enough, the
problem is worse (I think).

What should we do with other ->external checks? Just for example, don't
we need to chanhge collect_shared()

	- if (need_master && m->parent && !m->external)
	+ if (need_master && m->parent && !m->external &&
	      !come_on_this_mount_doesn_t_need_external(m))

?

And can_mount_now() looks suspicious too....

Oleg.